WASHINGTON — The number of people who have died in the U.S. after being shocked by police stun guns is growing rapidly, Amnesty International says in a report that catalogs 156 in the past five years.

Deaths after the use of Taser stun guns have risen from three in 2001 to 61 last year, the international human rights group said. Fourteen have died so far this year, it said, citing police and autopsy reports as well as press accounts.

The rise in deaths accompanies a marked increase in the number of U.S. law enforcement agencies employing devices made by Taser International of Scottsdale, Ariz. About 1,000 of the nation’s 18,000 police agencies used Tasers in 2001; more than 7,000 departments had them last year, according to a government study.

Police had used Tasers more than 70,000 times as of last year, Congress’ Government Accountability Office said.

Amnesty urged police departments to suspend the use of Tasers pending more study.

Taser decries studyTaser said the study was flawed, falsely linking deaths to Taser use when there has been no such official conclusion. “We remain concerned that Amnesty International continues to ignore the fact Taser systems have been medically cleared in nearly all of these incidents,” Taser vice president Steve Tuttle said.

Taser use early in a confrontation allows police to take people into custody and get medical attention sooner, Tuttle said. The company also says on its Web site that Tasers have saved more than 9,000 lives because police officers have been able to use stun guns instead of bullets. Tasers deliver a 50,000-volt jolt through two barbed darts that can penetrate clothing.

The Amnesty report is the latest study that raises concerns that use of a Taser — intended as a nonlethal alternative to a gun — can be fatal in certain circumstances, most often when the victim is using illegal drugs.

Police officers should use Tasers “only in circumstances where potentially lethal force is justified,” said William F. Schulz, executive director of Amnesty International USA. Schulz acknowledged that stun guns could be an effective part of a police arsenal, preferable in some cases to a nightstick or a gun.

Many of those who died were high on drugs, mentally ill or otherwise agitated. Many deaths in the past year occurred after victims were hit by Tasers at least three times and, in some cases, for prolonged periods, the report said.

In seven cases medical examiners or coroners determined that Taser use was a cause of death.

Among them:

Timothy Mathis, 35, had amphetamines in his system when sheriff’s deputies in Larimer County, Colo., shocked him between three and seven times during an altercation. Mathis went into cardiac arrest and died three weeks later. The coroner ruled the death a homicide, but the district attorney declined to press charges.

A Taser used by a Chicago police officer caused the death of Ronald Hasse, 54, in February 2005, according to the Cook County medical examiner’s office. Drug use was a contributing factor. Hasse was hit by a five-second electrical burst, followed by a 57-second charge, said Dr. Scott Denton, a deputy medical examiner.

In 16 other cases, authorities ruled that Taser use was a contributing factor in the death. In the bulk of the cases, victims died or lost consciousness soon after being shocked, but autopsies most often determined that illegal drugs were responsible or no cause of death was ascribed. Schulz said all 156 cases should be the subject of independent medical research.

Alternatives to stun gunsSome police agencies have tightened their rules on stun-gun use following Taser-related deaths.

In Nashville, Tenn., paramedics bearing tranquilizers are called on in place of stun guns to subdue suspects who may have a drug-induced condition known as excited delirium.

The change was made after Patrick Lee, 21, was shocked up to 19 times with a Taser by police officers who found him acting strangely outside a nightclub. Lee, who had drugs in his system and an enlarged heart, died two days later. Police officers in Las Vegas may no longer use Tasers on handcuffed prisoners and are discouraged from applying direct multiple shocks, following two deaths in 2004.

Apart from use by police, Taser said it has sold more than 115,000 devices to individuals since 1994. Stun guns are legal in 43 states, with varying restrictions, the company’s Web site says. They are illegal in Hawaii, Massachusetts, Michigan, New Jersey, New York, Rhode Island, Wisconsin and Washington, D.C., the company said.